Many linear olefins, particularly linear α-olefins, typically have a variety of valuable uses. For example, α-olefins, such as 1-hexene, can be used in hydroformylation (so-called “OXO” process) to produce oxygenated products like alcohols and aldehydes. In addition to finding uses in specialty chemicals or as intermediates, α-olefins also can be used in polymerization processes as either a monomer or co-monomer to prepare polyolefins, or other polymers. For example, it has been widely reported that 1-octene can form polymers or co-polymers, which may be used as effective drag reducing agents for transporting hydrocarbons in pipelines, It is therefore desirable to control the linearity of the product, or produce linear olefins, particularly linear α-olefins, in most oligomerization or polymerization processes.
It is well known that mono-olefins, particularly lower α-olefins, particularly ethylene, propylene, and 1-butene can be oligomerized (including dimerized and trimerized) and/or polymerized by using homogeneous or heterogeneous catalyst systems comprising compounds derived from transition metals such as titanium, zirconium, vanadium, chromium, nickel and/or other metals, either unsupported or on a support such as alumina, silica, silica-alumina, titania, other refractory metal oxides, and other similar materials. Even diene monomers such as 1,3-butadiene may be oligomerized or polymerized to give various products such cyclooctadienes. These polymerization catalyst systems frequently are used with an organometallic co-catalyst, such as organoboron, organoaluminum and/or organotin compounds.
Many catalyst systems are usually not very selective in the production of oligomeric or polymeric olefinic products in terms of molecular weight distribution, linearity of the carbon-carbon backbone, branching, location of the double bond(s) in the product, and incorporation of co-monomers, if any, into the product. Some reported homogeneous organometallic catalyst systems tend to have lower activities, higher consumptions of co-catalysts, but they can produce lower molecular weight oligomers or polymers with a narrow molecular weight distribution.
As a result, there is always a need of improving the catalyst systems to have better catalytic properties in terms of controlling specific oligomerization or polymerization of specific olefins or diolefins to produce products with the desired or targeted physical and chemical properties.